1. Technical Field
Present invention embodiments pertain to laser systems. In particular, present invention embodiments pertain to controlling transmissions of non-eye-safe laser signals from a laser sensing system to provide enhanced safety for nearby objects (e.g., persons, animals, etc.) situated outside the boundaries of the operating range of the laser sensing system.
2. Discussion of Related Art
Active laser sensors transmit a laser pulse to interrogate a substance, and detect a response from the substance to the transmitted laser pulse. For example, Raman sensors detect return or scattered light with constituent colors based on vibrational modes excited in the chemical compound being interrogated. Other sensors may employ other phenomenologies such as Laser Induced Breakdown (LIB) or Photo-thermal Induced physical phenomena. In each of these applications, the surface of the object must be illuminated with sufficient laser energy to stimulate the physical process. Accordingly, the power of the transmitting laser is increased in order to obtain a sufficient return signal from the substance. The laser power, temporal wave shape, and frequency of the laser determine the class of the laser, and the maximum permissible exposure for the laser source is determined by ANSI Z136.1-2000—American National Standard for Safe Use of Lasers. Typically, a safety exclusion zone (defined by the distance beyond which eye or skin damage is not possible) is many times greater than the operating range relevant to the laser sensor.
In certain applications, the laser characteristics can be controlled to enable the emitted light to always be eye-safe. These sensors typically have a very short effective range. Further, sensor operation may be performed in a region of the optical spectrum which is intrinsically safer. However, this is not always possible due to limitations of technology, or the attributes of the underlying phenomenology that the sensor employs (e.g., Raman scattering is most efficient in the ultraviolet region). An alternative technique to ensure safety is to require all personnel within the safety exclusion zone to wear appropriate personal protective equipment (PPE) (i.e., skin covering and eye safety glasses).
In many applications, especially those requiring detection at long ranges, the wavelength, pulse energy, or pulse shape of the illuminating laser may not be changed. Moreover, limiting personnel exposure, either by excluding all personnel or by requiring personnel to wear personal protective equipment (PPE), may not be possible. In some cases, the exclusion zone may be too large to even render this approach feasible.